Trace fossils Flashcards
What is another name for trace fossils?
Ichnofossils
What can trace fossils be used as?
Palaeoenvironmental indicators
What is endogenic trace fossils?
Made/ found within the rock (type of preservation)
What is epirelief trace fossil preservation?
Preserved on the top of beds
What is hyporelief?
Located at the base of beds
What is full relief?
Located within beds
What are exogenic traces?
Made on the sediment surface
How are full relief trace fossils preserved?
burrow preserved in 3d
What is another name for epirelief and hyporelief?
semi relief
Where is hyporelief most common?
Interbedded sands and muds
Where is an example of hyporelief?
Aberystwyth Grits (Silurian)
What are natural casts, true track, undertracks? (trace fossils)
Natural - made by infilling of original track
True - actual imprint
Undertrack - dent in sediment by animal pressure
What is the bias with trace fossils/ undertracks?
Bias towards heavier that can leave a greater impression
What is an example of undertrack preservation?
Sauropod footprints in the Morrison Formation Colorado
What problems are associated with trace fossil identification?
Single organism can produce many trace fossils
Different organism can produce similar trace fossils
What do invertebrate trace fossils names tend to reflect?
Morphology of trace (shape and ornamentation)
What can be used to describe the morphology of trace fossils?
Ichnogenus and Ichnospecies
How many trace fossils are produced by the Uca (modern day fiddler crab)?
4 traces
What are the trace fossils produced by Uca?
Psilonchnus - domichnion (living burrow)
Diplichnites - repichnion (walking trail)
Pascichnion - grazing trail
Coprolites - feacal pellets
What is the name for the resting trace? (cubchnia)
Rusophycus
What is the problem associated with identifying resting traces?
Originally thought just trilobites hunkering down on sediment but found other organisms can produce aswell
What are some examples of organisms which can produce resting fossils?
Polychaete worms
Snails
Brachiopod shrimps
Trilobites
What is repichnia?
walking or crawling trace
What is an example of a crawling trace?
Cruziana - Ordovician Anzaldo Fm Bolivia
What is an example of domichnion? (living burrow)
Arenicolites
What do arenicolites produce?
U shaped burrows which makes a worm cast and depression
What do arenicolite worm burrows do to the rock chemistry?
Anoxic rock is made oxygen rich by when oxygenated water is pulled into the sediment